Infection of Erynia blunckii (LAK. ex ZIMM.) REM. et HENN. (Entomophthorales : Entomophthoraceae) in the Diamond-Back Moth, Plutella xylostella L. (Lepidoptera : Yponomeutidae)

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Abstract
An entomogenous fungus was isolated from Plutella xylostella larva and identified as Erynia blunckii. The fungus penetrated the host cuticle by germ tubes which were produced on conidia that individually were in direct contact with the cuticle. Conidia located on the outer region of a cluster formed secondary conidia which did not enter the cuticle. The germ tubes on the cuticle were of various shapes : (1) hypha with thickened penetration point, (2) hypha with dual-bulb formation, and (3) screw-like slender hypha. Appressorium and infection cushion were never observed. A transparent zone developed in the cuticle surrounding the invading hypha. Within the hemocoel, the penetrated hyphae broke up into hyphal bodies, multiplied, and invaded mostly fat body and to a lesser degree the muscle, hypodermis, and endocuticle before larval death. The fungus invaded and disintegrated most of the other solid tissues and organs after the death of the larva.